“Maybe someone is overly brusque, or is always putting urgent or cc’ing everything,” Mr. Purdy says. “Bcc is almost always a dangerous idea. Transparency is important—it prevents you from seeming sneaky. If you are bcc’ing someone to get someone else in trouble, you are being the office jerk.”

Above the Law considered email etiquette in a 2010 blog post. Pet peeves include people who write complete emails in the subject line and people who have long signature lines touting their involvement in clubs and committees that no one cares about.

The Wall Street Journal lists other types of people who annoy. They include people who ingratiate themselves with the boss at the expense of co-workers, people who are overly negative, and people who are messy in shared spaces.